A patient develops sudden cardiovascular collapse with refractory VF after an inadvertent intravascular injection during an interscalene brachial plexus block. The anaesthetic agent most likely responsible and the specific first-line lipid rescue dose is:

• A Lignocaine; 20% intralipid 1.5 mL/kg IV bolus followed by infusion at 0.25 mL/kg/min
• B Ropivacaine; 10% intralipid 3 mL/kg IV bolus followed by infusion at 0.5 mL/kg/min
• C Bupivacaine; 30% intralipid 1 mL/kg IV bolus with no infusion required
• D Bupivacaine; 20% intralipid 1.5 mL/kg IV bolus followed by infusion at 0.25 mL/kg/min ✓

Explanation

Bupivacaine has the highest cardiotoxicity among local anaesthetics due to its high lipid solubility and slow dissociation from sodium channels ('fast-in, slow-out' kinetics), producing refractory ventricular fibrillation and difficult resuscitation. The AAGBI Lipid Rescue protocol recommends 20% Intralipid: 1.5 mL/kg IV bolus over 1 minute, then infusion at 0.25 mL/kg/min, repeating the bolus up to twice if cardiovascular stability not restored (maximum cumulative dose 12 mL/kg). The 'lipid sink' mechanism sequesters bupivacaine in a lipid phase, reducing free plasma concentrations. Ropivacaine and lignocaine have lower cardiotoxicity; 10% and 30% intralipid are incorrect concentrations.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.